1. Field of the Invention
The invention relates to an ink-jet print head and a method for fabricating the same, and more particularly to an ink-jet print head with a chamber sidewall heating mechanism for forming bubbles within a chamber to eject an ink drop.
2. Description of the Related Art
Recently, ink-jet printers have been gradually popularized, the cost of the ink-jet printer is gradually decreased, and the printing effect is gradually enhanced. On the other hand, since the cost of the color laser printer is still high, the ink-jet printer plays a more important role in the color printing market.
The core technology of the ink-jet printer mainly resides in that the property of the ink-jet print head, which strongly relates to the printing quality. The ink-jet print heads may be mainly divided into a thermal bubble type and a piezoelectric type according to the principle of ejection. The invention aims at the thermal bubble type ink-jet print head. The main principle of the thermal bubble type ink-jet print head is to utilize at least a heater to evaporate the ink to generate bubbles. Sequentially, the pressure of the bubble ejects the ink drop onto the paper so as to form the desired image.
In the prior art, all the heater structures in the thermal bubble type ink-jet print heads reside on either bottom or top, in parallel to the silicon substrate surface, of the chamber. FIG. 1 shows the partially schematic illustration of the prior art thermal bubble type ink-jet print head. Referring to FIG. 1, the ink-jet print head 100 includes a silicon substrate 101, an insulation layer 102 on the silicon substrate 101, a heating resistor 103 on the insulation layer 102, conductive wires 104 and 105 on the heating resistor 103, and a nozzle plate 106 above the conductive wires 104 and 105. An air chamber is formed between the nozzle plate, the heating resistor, and the sidewall, and the ink may be fed into the chamber through the micro channel (not shown) connecting the chamber and the ink reservoir. Thus, an ink chamber 107 is located above the heating resistor 103. The conductor wires 104 and 105 are applied with a voltage such that the current flows through the heating resistor 103 to heat up the ink above it. When the temperature of the heater gradually increases and is higher than the evaporation point of the ink, the local ink above the heater is thus evaporated to form a gas bubble and gradually the bubble grows larger and larger accompanying the higher and higher heater temperature. Finally, a net pressure due to the growing bubble pushes the residual, non-vaporized ink toward the orifice 108 and out of the orifice to the paper sheet to finish the printing mechanism.
In this prior art, there are several problems needed to be overcome. First, the generally adopted heater material (TaAl) is incompatible with the commercial IC processes, that means the heater fabrication process can not be finished in the commercial IC foundry and extra-cost is increased to define the heater process in a special foundry for this purpose. Furthermore, the micro-channel is manufactured using the thick photoresist technology, which is also incompatible with the commercial IC fabricating processes, and the resolution of the thick photoresist is poor. The geometric shape of the micro-channel relates to the refill of ink and the operation property. Typically, the micro-channel has a very narrow opening connected to the chamber and has a V-shape-like fan-out connected to the main channel (not shown), in which the fabrication tolerance must be strictly controlled. Otherwise, the poor ink-jet printing property may be caused. Besides, the heater residing on the bottom surface of the chamber has the problem that the generated heat may be conducted into the silicon substrate due to the large contact surface area between the heater and the substrate. To solve that problem, a thick thermal isolation layer is generally placed there between the heater and the silicon substrate. This would cause another problem of cross talk between two heaters when the heaters density is increased (the printer resolution increases).